UBC Theses and Dissertations
Therapy-related hepatic mitochondrial dysfunction in patients co-infected with human immunodeficiency virus and hepatitis C virus and in HepG2 cells Taillefer, Rachel Elise
Background: Co-infection with HIV and hepatitis C virus (HCV) worsens liver disease and decreases highly active antiretroviral therapy (HAART) tolerability. HAART usually includes two nucleoside reverse transcriptase inhibitors (NRTIs) and a protease inhibitor (PI) or a non-NRTI (NNRTI). NRTIs, particularly D-NRTIs, can induce mitochondrial DNA (mtDNA) depletion, deletions or mutations and lead to mitochondrial dysfunction. Multi-drug resistance protein-1 (MDR1) transports drugs across cellular membranes and may modulate toxicity. This project investigated HAART-related mitochondrial toxicity in liver tissue from HIV/HCV co-infected individuals and in human hepatic (HepG2) cells. Hypotheses: 1) Patients ON-HAART will have altered pathology scores, mtDNA quantity/deletions and mt-mRNA/MDR1-mRNA levels compared to patients OFF-HAART, and these will be influenced by type of HAART. 2) Treatment with the d-NRTI didanosine (ddI) and the PI saquinavir (SAQ) will alter HepG2 cell viability, population doubling time (PDT) and mtDNA content. Methods: Double-liver biopsies were collected from HIV/HCV co-infected individuals. One sample was used to score pathology, the other to extract DNA and RNA. mtDNA quantity, mt-mRNA and MDR1-mRNA levels were investigated by quantitative-PCR and mtDNA deletion by long-template PCR. Measurements were compared between individuals ON- versus OFF-HAART, on D-NRTI versus other NRTIs and on PI versus NNRTI. HepG2 cells were exposed to ddI and SAQ. Cell viability, PDT and mtDNA content were investigated. Results: Individuals ON-HAART (N=34) were similar in age, gender and HCV genotype to those OFF-HAART (N=18), and the groups did not differ significantly in pathology score, mtDNA quantity/deletions or mt-mRNA/MDR1-mRNA levels. The same was true for individuals on D-NRTI (N=6) versus other NRTIs (N=28) and on PI (N=17) versus NNRTI (N=8), except that individuals on PI were older (p=0.044) with higher mt-mRNA levels (p=0.015). Treatment of HepG2 cells with ddI lowered mtDNA content while SAQ decreased PDT. Addition of a second drug (SAQ or ddI) exacerbated these effects. ddI transiently decreased viability. Conclusions: The lack of differences between the ON- and OFF-HAART groups supports previous observations that HAART is not associated with increased hepatic mitochondrial toxicity although the cell culture findings suggest complementary toxicity upon co-exposure to ddI/SAQ. This study may inform management of HIV/HCV co-infected individuals.
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